CodeForces 351A Jeff and Rounding

 1 // File Name: 351a.cpg
 2 // Author: darkdream
 3 // Created Time: 2015年03月08日 星期日 12时21分23秒
 4 
 5 #include<vector>
 6 #include<list>
 7 #include<map>
 8 #include<set>
 9 #include<deque>
10 #include<stack>
11 #include<bitset>
12 #include<algorithm>
13 #include<functional>
14 #include<numeric>
15 #include<utility>
16 #include<sstream>
17 #include<iostream>
18 #include<iomanip>
19 #include<cstdio>
20 #include<cmath>
21 #include<cstdlib>
22 #include<cstring>
23 #include<ctime>
24 #define LL long long
25 
26 using namespace std;
27 int a[5000];
28 const double eps = 1e-8;
29 int main(){
30    int n ; 
31    scanf("%d",&n);
32    double sum = 0 ; 
33    int n0 = 0 ; 
34    for(int i = 1;i <= 2*n;i ++)
35    {
36       double tmp;
37       scanf("%lf",&tmp);
38       int x = (tmp*1000+eps);
39       a[i] = x % 1000;
40       if(a[i] == 0 )
41           n0 ++ ; 
42       sum += a[i]*1.0/1000;
43    }
44    double  ans = 1e9 ;
45  //  if(n == 32)
46    //printf("%f %d %d\n",ans,min(2*n-n0,n),n0);
47    for(int i = max(0,n-n0);i <= min(2*n-n0,n) ;i ++)
48        ans = min(ans,fabs(sum-i));
49    printf("%.3f\n",ans); 
50 return 0;
51 }